The World Wildlife Fund (WWF) on Monday urged the Mexican government to impose a complete ban on fishing in the habitat of the vaquita porpoise, saying it is the only way to save the critically endangered species from extinction.

An international team of experts recently warned that fewer than 30 vaquita porpoises have are left in the upper Gulf of California, which is the only place for the endangered mammal to live.

Earlier this year, Mexican government officials announced a plan to catch the remaining vaquitas and keep them in pens for protection and breeding. But, the WWF argued that isn’t the right answer to protect the species.

In its newly released statement, the WWF said, “The only way to save the vaquita from extinction is for the Mexican government to immediately and indefinitely ban all fisheries within its habitat.”

Mexico has already banned gillnet fishing in the habitat of the vaquita porpoise, but that has proved quite hard to enforce. Banning all fisheries within vaquita’s habitat would be politically as well as economically costly for the government.

The WWF also noted that the Mexican government’s catch-and-enclose plan is very risky because the few remaining female vaquita porpoises could die during capture, dooming the species. Moreover, this critically endangered species has never been held or bred in captivity.